WE-E-BRB-08: Establishing Comprehensive Quality Assurance Program for Volumetric Modulated Arc Therapy - Clinical...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Quality Assurance

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a complex radiotherapy technique requiring rigorous quality assurance (QA).
• Traditional VMAT QA methods like gamma analysis using ArcCHECK™ and treatment planning system (TPS) dose comparison have limitations in identifying specific sources of discrepancies.
• Existing QA protocols often cannot determine how QA failures impact patient treatment or pinpoint the root cause of deviations.

Purpose of the Study:

• To validate the clinical effectiveness of Control Point Analysis (CPA) software for VMAT QA.
• To establish a comprehensive QA program for VMAT treatment using CPA and 3DVH™ software.
• To assess the ability of CPA to identify sources of dose discrepancies beyond standard gamma analysis.

Main Methods:

• Control Point Analysis (CPA) and 3DVH™ software were evaluated using eight VMAT cases (prostate, brain, head&neck) and TGI 19 phantom.
• VMAT plans were divided into 24 sub-arcs per treatment arc, with doses exported for CPA analysis.
• Gamma analyses (3mm/3%) were performed comparing ArcCHECK™ doses, single arc doses, sub-arc doses, and 3DVH™-estimated patient doses (Planned Dose Perturbation™ algorithm).

Main Results:

• ArcCHECK™ composite dose analysis generally aligned with CPA sub-arc analysis.
• 3DVH™ demonstrated a higher passing rate in voxel-by-voxel dose comparisons.
• CPA successfully identified specific sources of QA failures, including mechanical errors (e.g., leaf motion) and dosimetric modeling errors (e.g., beam spot size, dynamic leaf gap), which were not evident in composite dose comparisons.

Conclusions:

• Control Point Analysis (CPA) significantly enhances VMAT QA by providing detailed insights into dose discrepancies without increasing user workload.
• Integrating CPA and 3DVH™ enables a comprehensive VMAT QA program that maps composite dose passing rates, estimates the clinical impact of discrepancies, and identifies their origins.
• CPA's ability to detect subtle errors, such as those caused by a failing multi-leaf collimator (MLC), improves the overall reliability of VMAT treatments.